Vapor electric device



Nov. 7, 1939. A, H. ToEF-FER" VAPORELECTRIC DEVICE Filed April 14, 1938nNvENTQR WITNESSES:

' .ATTORNEY Patented Nov. 7, 1939 iJNiTED STATES Edwin@ VAPOR ELECTRICDEVICE Adolph Iii. Toepier, Wilkinsburg', Pa., assigner tc WestinghouseElectric & Manufacturing Company, East Pittsburgh, Pa., a corporation oPennsylvania Application April 14,

7 Claims.

My invention relates to a make-alive electrode for a vapor electricdevice and more particularly to electrodes of the high resistance typeand the method of making the same.

In the operation of vapor electric discharge devices, it has been foundadvantageous to employmake-alive electrodes of some high resistancematerial such as boron carbide, carborundum, graphite, etc., to initiatean arc at the beginning of each conducting period in the rectifier.Recently, engineers have been designing and constructing electrodes tominimize the operating currents and voltages required to start an arc insuch rectifiers. Tests have been made using irregularly shaped pieces ofsome high resistance material as make-alive electrodes, but considerabledifficulty has been experienced with such electrodes which mayheretofore have been unusable due to the fragile nature of the materialand the difficulties of mounting the same.

In the male-alive electrode according to my invention, I utilize aquartz tube or some similar refractory material capable of withstandinghigh temperatures and heat shock. A narrow slit in the order ofone-sixteenth of an inch is made in the side of the tube and then lledwith irregular shaped pieces of boron carbide, carborundum or graphite.I select the pieces of the resistance material large enough not to passthrough the slit, yet capable of projecting out through the slit. Asuitable conductor for carrying current to the high resistance particlesis extended down into the quartz tube so as to be in contact with thebroken pieces of resistance material. Due to the buoyancy effect ofmercury when such make-alive electrodes are immersed therein, a goodcontact between the conductor and the resistance material is maintained.

It is, therefore, an object of my invention to provide a make-aliveelectrode requiring a low operating current to initiate the arcdischarge.

Another object of my invention is to provide scription taken inconjunction with the accompanying drawing, in which:

Figure l represents diagrammatically a vapor discharge device of a typewith which my im- 55 proved make-alive electrode may be utilized;

1938, Serial No. h95?? (Cl. Z50-27.5)

of my invention comprises an evacuated container 3 of glass or othersuitable material having an anode 5 sealed therein. Disposed with re*spect to the anode 5 and adapted to cooperate with it in conducting anarc discharge through the container 3, I show a cathode l of vaporizablematerial such as mercury. Suspended above' the cathode 'l and having aportion permanently projecting below the surface of the cathode "l ismounted a make-alive electrode il of the type which I shall fullyexplain. The anode 5 and the cathode 'l are externally connected with aload Il and some suitable source of supply potential i3. Likewise, themake-alive electrode 9 is connected externally through a suitableunidirectional device !5, such as half-wave rectier, with a grid controladapted to pass current to the make-alive electrode Si at apredetermined time with respect to the anode potential.

In constructing a make-alive electrod-e ii acn cording to Fig. 2 of myinvention, I employ a quartz tubing l1 opened at one end. Substantiallynear the closed portion of the tube il, I bore a narrow slit i9 having awidth in the neighborhood of one-sixteenth of an inch. The slit lil neednot be of any particular length, but I prefer one having such a lengththat a portion of the slit i9 remains below the cathode surface l aswell as an approximately equalv portion above .the surface to compensatefor variation in the mercury level. It is to be understood, however,that I do not wish to limit my construction to one slit lg for it may bedesirable to have several slits i9. Suitable size particles is of somehigh resistance material such as boron carbide are inserted into thetube ll to such a depth as to cover the slit portion it of the quartztube il, It is a necessary property of a satisfactory make-alivematerial iii that it shall not react chemically with the mercury in thepresence of an arc discharge, nor should the make-alive material i8become wet by the mercury.

In preparing the make-alive material l@ contemplated by my invention, Itake a rod of boron carbide and break it up into pices of a suitablesize and screen the broken pieces to free the nely pulverized particlesfrom those I intend using. The quartz tubing I1 is lled with manyirregular shaped pieces of the starting material I8, so that the slit I9is substantially covered. It may be desirable to shape the tubing i1 atthis point so as to cause a portion of the boron carbideparticles I8 toprotrude out from the slit I9, thereby having an active portion exposedto the mercury cathode 'I when the makealive electrode S is mounted inplace. A suitable rod ZI of conducting material is extended into theopen end of the tubing I1 and is brought into contact with the startingmaterial I8. The rod 2| in Fig. 3 of my invention likewise may have aslit in line with the slit I9 of the quartz tubing I1.

According to Fig. 4 of my invention, I provide a make-alive electrode 9of the type brought in through the mercury pool 1. A rod 23 of Kovar ormolybdenum, having a stem portion 25 and a cup portion 21, is brought upthrough the mercury pool 1, so that the cup portion 21 protrudesslightly above the mercury surface 1. An insulating covering 29 of glassseparates the rod 23 from the mercury in all but a slit portion I9 ofthe cup 21 which I maintain exposed to the cathode 1. The insulatingcovering 29 serves in addition as a vacuum seal for the make-aliveelectrode 9. Disposed in the base of the cup portion 21 of themake-alive electrode 9 is some insulating material 3l, preferably glass.The glass insulator 3l may cover a side portion of the cup 21, butshould be maintained below the mercury level. Particles of boron carbideI8 ll the cup portion 21, which I maintain closed at the projected end.A Kovar flange 33 sealed to the insulating covering 29 may be welded orcopper soldered to the metal container 35 at the bottom thereof.

In the operation of the arc discharge device 2, an exciting potential isapplied to the make-alive electrode 9 and an aro is struck between themercury cathode 1 and an active portion of the boron carbide particlesI8 which protrude out through the slit I9. Upon proper conditions ofpotential,l the arc immediately expands into a greater arc which willtransfer quickly to the anode 5 if the latter is sufliciently positive.Several of the make-alive electrodes 9 tested operated on lO amperespeak current with a peak potential of 35 volts.

While I have shown and described specific embodiments of my invention,it will be apparent to those skilled in the art that many changes andmodioations can be made therein without departing from the true spiritof my invention or the scope or the appended claims.

I claim as my invention:

1. A make-alive electrode comprising a container of insulating material,a slitted opening in a lower portion thereof and a plurality ofindependent loose particles of high resistance material in saidcontainer, the size of said particles being such that only a portion ofseveral protrude out from said slitted opening and a conductor inContact With only a portion of said particles.

2. A make-alive electrode for an electric arc discharge devicecomprising a container of insulating material, a mass of loose particlesof resistance material in said container, a slitted opening in saidcontainer adjacent said particles, the width of said slit being lessthan the size of said resistance particles and a conductor extendinginto said container and being in contact with some of said particles.

3. A make-alive electrode for an electric arc discharge devicecomprising a hollow cylindrical body of non-conducting material closedat one end, a slitted aperture near the closed portion oi' said body, aquantity of loose particles of high resistance material lling asubstantial portion of said body and a conducting body extending intothe open end of said non-conducting body and in contact with saidresistance particles.

4. In combination with a mercury-pool discharge device, a make-aliveelectrode comprising a` quartz container substantially lled with looseparticles of boron carbide, a vertical slit in a lower portion of saidcontainer, said boron carbide particles capable of protruding from saidslit and a conductor extending into said container, said conductor beingin contact with at least some of said boron carbide particles but out ofcontact with said mercury-pool.

5. A vapor-electric device comprising an evacuated container, apool-type cathode therein, an

anode cooperating with said cathode, a makealive electrode dipping intosaid cathode, said make-alive electrode comprising a container ofnon-conducting material, a plurality of loose particles of resistancematerial in a lower portion of said container, a slitted opening in thatportion of said container dipping into said mercurypool, an activeportion of said resistance particles extending through said slit and aconductor in contact with part of said particles.

6. In an electric arc discharge device comprising an evacuatedcontainer, an anode and a mercury cathode therein, a make-aliveelectrode extending upwardly through said cathode, said make-aliveelectrode comprising a stem portion and a cup portion, said cup portionpartially projecting above the surface of said cathode, an insulatordisposed in the base of said cup portion of said make-alive electrode, aslit in said cup portion, an insulating covering separating said Qmake-alive electrode from said cathode in all but said slit portion andproviding a vacuum-tight seal for said make-alive electrode and aplurality of loose particles of high resistance material in said cupportion, an active portion of said resistance particles being exposed tosaid cathode by way of said slit.

'7. A make-alive electrode for a vapor-electric device comprising acontainer of insulating material, a narrow longitudinal opening alongone side of said container, a plurality of loose particles of resistancematerial in said container and partially extending through said opening,and a conductor extending into said container and making contact with atleast one of said particles.

ADOLPH H. TOEPFER.

